Mass killings generally occur in settings of armed conflict where it is very difficult or impossible to collect official data on births, deaths and marriages. In this video, DIEGO ALBUREZ-GUTIERREZ confronts this challenge by focusing on the mass killings of the Maya Achi people which took place during the Guatemalan Civil War in the 1980s. Using a novel approach, the “Extended Genealogy Method”, Alburez-Gutierrez reconstructed the demographic history of the affected population over the last 60 years from interviews with relatives of the victims. This project, the first in-depth quantitative study of the genocide in Guatemala, has evident historical significance. It also provides empirical insights into the effects of mortality shocks on population dynamics and introduces a scalable data collection tool.